Specific Weight of Basalt, Its Properties, Characteristics and Weight

Basalt is an extrusive igneous rock consisting of ore minerals such as magnetite and titanomagnetite, basic plagioclase, iron-magnesium minerals and, comparatively rarely, olivine, nepheline and leucite. Depending on crystal size and properties, basalt is commonly divided into:

• dolerite, which may be fine-, medium- or coarse-grained;
• anamesite, which occurs as a fine-grained variety;
• porphyrite, which differs from standard varieties because of changes caused by secondary hydrothermal and thermal processes. It is also known as diabase porphyrite.

Basalt is used mainly in its natural form. However, some basalt rocks with increased alkalinity can be used after melting. Such material is called fused basalt. Unlike natural basalt, it has a finer-grained structure and high resistance to mechanical damage, chemical and thermal resistance, and good electrical insulation properties.

Table of Specific Weight of Basalt

Because basalt is a complex rock, it is impossible to calculate its specific weight manually without special equipment. Such measurements are carried out in special chemical laboratories. However, for most work, the average specific weight is sufficient. For natural basalt, the specific weight ranges from 2.7 to 3.2 g/cm3. For basalt glass, the value is slightly different and ranges from 2.7 to 2.85 g/cm3.

For convenient reference and calculation, the table below gives values for the weight of basalt.

Properties of Basalt

The structure of basalt is porphyritic or aphyric. In its natural form, it appears as a glassy and cryptocrystalline mass. The texture is mostly massive, less often porous, slag-like or vesicular. The mass is uncrystallized volcanic glass permeated with magnetite particles and a mixture of microscopic inclusions of pyroxene, olivine and plagioclase, less often hornblende.

A characteristic feature of basalt is its hexagonal-prismatic columnar structure. The columns may reach tens of meters in length and are oriented perpendicular to the surface. In the upper parts of basalt flows, porosity increases as volcanic gases escape from the lava.

By its characteristics, basalt has the following indicators:

• porosity from 0.5 to 1.5%;
• water absorption by volume from 0.5 to 14%, by weight from 0.2 to 0.4%;
• compressive strength of dry basalt from 2640 to 3200 kg/cm2, wet basalt 2500 kg/cm2, diabase from 1800 to 2700 kg/cm2, fused basalt from 3000 to 9158 kg/cm2.